Modelling the alumina abundance of oxygen-rich evolved stars in the Large Magellanic Cloud

Abstract

In order to determine the composition of the dust in the circumstellar envelopes of oxygen-rich asymptotic giant branch (AGB) stars we have computed a grid of modust radiative-transfer models for a range of dust compositions, mass-loss rates, dust shell inner radii and stellar parameters. We compare the resulting colours with the observed oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC) sample, finding good overall agreement for stars with a mid-infrared excess. We use these models to fit a sample of 37 O-rich AGB stars in the LMC with optically thin circumstellar envelopes, for which 5$-$35-$\mu$m Spitzer infrared spectrograph (IRS) spectra and broadband photometry from the optical to the mid-infrared are available. From the modelling, we find mass-loss rates in the range $\sim 8\times 10^{-8}$ to $5\times 10^{-6}$ M${}_{\odot }{\mathrm{yr}}^{-1}$, and we show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron provides a good fit to the observed spectra. Furthermore, we show from dust models that the AKARI [11]$-$[15] versus [3.2]$-$[7] colour-colour diagram, is able to determine the fractional abundance of alumina in O-rich AGB stars.

22 pages, 17 figures, accepted MNRAS

References in corpus (14)

• An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
• Spitzer SAGE survey of the Large Magellanic Cloud II: Evolved Stars and Infrared Color Magnitude Diagrams
• A close halo of large transparent grains around extreme red giant stars
• The dust condensation sequence in red super-giant stars
• The Magellanic zoo: Mid-infrared Spitzer spectroscopy of evolved stars and circumstellar dust in the Magellanic Clouds
• The Mass-Loss Return from Evolved Stars to the Large Magellanic Cloud IV: Construction and Validation of a Grid of Models for Oxygen-Rich AGB Stars, Red Supergiants, and Extreme AGB Stars
• A Spitzer IRS Spectral Atlas of Luminous 8 micron Sources in the Large Magellanic Cloud
• Tracing the development of dust around evolved stars: The case of 47 Tuc
• On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants
• The Mass-Loss Return from Evolved Stars to the Large Magellanic Cloud II: Dust Properties for Oxygen-Rich Asymptotic Giant Branch Stars
• The LMC's Top 250: Classification of the Most Luminous Compact 8 micron Sources in the Large Magellanic Cloud
• Broad-band photometric colors and effective temperature calibrations for late-type giants. II. Z<0.02
• AKARI Infrared Camera Survey of the Large Magellanic Cloud. I. Point Source Catalog
• ISO Mid-Infrared Spectroscopy of Galactic Bulge AGB Stars

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• An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-Redshift AGB Analogs
• On the alumina dust production in the winds of O-rich Asymptotic Giant Branch stars
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• J-PLUS: Stellar Parameters, C, N, Mg, Ca and [α/Fe] Abundances for Two Million Stars from DR1
• Red supergiant stars in the Large Magellanic Cloud. II. Infrared properties and mid-infrared variability
• Probing the dusty stellar populations of the Local Volume Galaxies with JWST/MIRI
• Understanding the evolution and dust formation of carbon stars in the LMC with a look at the JWST
• The dustiest Post-Main sequence stars in the Magellanic Clouds
• Evolved stars in the Local Group galaxies - III. AGB and RSG stars in Sextans A
• Characterizing the Population of Bright Infrared Sources in the Small Magellanic Cloud
• Near-Infrared Stellar Populations in the metal-poor, Dwarf irregular Galaxies Sextans A and Leo A
• Three-component modelling of C-rich AGB star winds V. Effects of frequency-dependent radiative transfer including drift
• Understanding dust production and mass loss on the AGB phase using post-AGB stars in the Magellanic Clouds
• Discovery of stars surrounded by iron dust in the LMC
• Infrared Properties of Asymptotic Giant Branch Stars in Our Galaxy and the Magellanic Clouds
• Optical properties of non-stoichiometric amorphous silicates with application to circumstellar dust extinction
• Characterization of M-stars in the LMC in the JWST era
• How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions -- The case of EP Aqr
• Do evolved stars in the LMC show dual dust chemistry?
• Infrared variable stars in the compact elliptical galaxy M32
• Optical properties of amorphous alumina dust in the envelopes around O-rich AGB stars
• The dusty envelopes of asymptotic giant branch stars with ultraviolet excesses
• The Nearby Evolved Stars Survey II: Constructing a volume-limited sample and first results from the James Clerk Maxwell Telescope